The branching of axons is a fundamental aspect of neurodevelopment and the response of the nervous system to injury. This proposal seeks to understand the role of a protein called Sarm1 in developmental and injury induced axon branching. Sarm1 has been involved in axon degeneration following injury, but our preliminary data unveils a novel role for Sarm1 as a repressor of axon branching. The project has two Aims focused on elucidating how Sarm1 impacts the cytoskeleton underlying branching, and whether Sarm1 is involved in injury-induced axon branching. Completion of the project will advance our understanding of the mechanism of axon branching and identify a novel role for Sarm1 in the response of the nervous system to injury.